The present invention relates to the arrangement of recorded data on an information recording medium. More particularly, it relates to an information recording medium including information arranged thereon so as to allow restricted writing and reading in a commonly current write and read drive, and a system for performing restricted write and read operations on and from the information recording medium.
One example of a conventional optical recording system will be described with reference to FIGS. 3 and 5 as one example of an information recording system.
FIG. 3 shows a block diagram of a conventional optical write and read drive. The light beams emitted from a laser 25 (with a wavelength of about 660 nm for a DVD-RAM), which is a part of a head 2, are collimated into a nearly parallel light beam 22 through a collimating lens 24. The light beam 22 is applied onto an optical disk 11 through an objective lens 23 so as to form a spot 21. Thereafter, the reflected light beams are guided through a beam splitter 28, a hologram element 29, or the like, to a servo detector 26 or a signal detector 27. A signal from each detector is subjected to an add/subtraction process to become a servo signal, such as a tracking error signal or a focus error signal, which is then inputted to a servo circuit. The servo circuit controls the positions of a driving means 31 of the objective lens 23 and the whole optical head 2 based on the tracking error signal and focus error signal that has been obtained, so that the optical spot 21 is positioned in an objective writing and reading area. An added signal from the detector 27 is inputted to a signal reproduction block 41. In a signal processing circuit, the inputted signal is subjected to a filtering process and a frequency equalizing process, and then is subjected to a digitization process. The digital signal thus subjected to a digitization process is processed by an address detector and a demodulation circuit. Based on the address signal detected by the address detector, a microprocessor calculates the position of the optical spot 21 on the optical disk 11 and controls a position control means, thereby to position the optical head 2 and the optical spot 21 at an objective recording unit area (sector).
If the instruction from a host to the optical write and read drive is a writing instruction, the microprocessor receives recording data from the host and stores it in a memory, while controlling the position control means to position the optical spot 21 at a position in an objective recording area. The microprocessor checks that the optical spot 21 has been properly positioned in the recording area by an address signal from the signal reproduction block 41, and then controls a laser driver and the like to write the data in the memory on an objective recording area.
An address signal is arranged in every information recording unit area, at the beginning portion of the recording unit area, as shown in FIG. 6. Therefore, it is possible to check the position of the optical spot immediately before writing by detection of the address signal.
FIG. 5 shows an example of the flow of operation of an optical recording system for driving the DVD-RAM disk specified in International Standard ISO/IEC-16824, or the like, which is a rewritable DVD or DVD-RAM representing one example of the optical recording system described above.
When a disk is loaded, or the power of the optical recording system is turned on, first, the optical recording system performs a process for discriminating the types of media. In general, it has a function of reading a CD-ROM or DVD-ROM which is a read-only medium, in addition to the DVD-RAM medium. Therefore, the optical recording system first performs a media type discrimination process to discriminate which one of the types described above the medium corresponds to. Individual systems perform the discrimination process in mutually different ways. For example, some systems discriminate the types of media from the analogue characteristics of the reflectance and the reproduced signal, such as the focus error signal, and other systems read a physical information area provided on a disk substrate and then discriminate the types of media based on the contents (data).
If the optical recording system identifies the type of the medium as a rewritable type, i.e., a DVD-RAM, first, it checks the recorded contents of a defect management information area, and the like, and thereby checks whether the optical disk has been physically formatted. If the optical disk has not been physically formatted, a wait period is initiated until a physical format command is issued from a host or a user.
If the optical disk has been physically formatted, the optical recording system performs a process of preparation for writing, such as a calibration process or logical consistency verification, and then it enters a wait state for a command from a user or host. Upon receiving some command, the optical recording system checks the type of the command. Then, if it is a write command, the optical recording system performs a writing process. For commands of read, format, unloading of the disk, and the like; the optical recording system performs respective corresponding processes. In general, these processes are normally terminated. However, in case of an unsuccessful write operation for an unexpected reason, the system performs an error handling process, such as retry or replacement.
In general, with a DVD-RAM, during the writing process, whether the recording data has been normally written or not is checked by actually reading the recorded data. If required, replacement is performed by using another recording unit area, thereby to enhance the reliability of the recorded data. The management information on the reallocation of recording areas due to the replacement is written in a specific area (defect management area).
Thus, the DVD-RAM is an optical recording system having very high reliability. However, since the recorded data is basically freely rewritable, it is not possible to eliminate the possibility that the important data already recorded is erased or rewritten due to a wrong operation by a user, a malfunction of the host, or the like.
Further, replacement is performed on the following precondition: even if rewriting processes are performed for a sufficiently larger number of times than the number of defects storable in the defect management area, it is possible to perform writing and reading with no problem.
As one method of protection, there is a so-called write protection function. However, the write protection can be freely revoked by a user. Accordingly, it is still impossible to prevent data corruption by the wrong operation of a user.
An example of a magneto-optical disk will be described as a proposal for overcoming such a problem. The magneto-optical disk is a rewritable storage medium that is capable of erasing and rewriting user data with respect to a user data area including user data recorded therein. However, there is a demand for this to be used as a WORM type storage medium not capable of erasing and rewriting user data.
For example, with a CCW method specified in International Standard ISO-1EC11560 (or a MO-WORM method), media type identification data indicative of the type of the magneto-optical disk is included in a control information area provided in an area outside the user data area of the magneto-optic disk. As a result, it is possible to identify whether the magneto-optical disk is of a rewritable type or a WORM type based on the media type information.
The magneto-optical disk drive is so configured that, if the WORM type magneto-optical disk is loaded therein, the erasing operation and the rewriting operation are not to be performed with respect to the user data area including user data already written therein. Namely, the magneto-optical disk, which is originally of a rewritable type, is provided with a write protection function for preventing erasing and overwriting. Consequently, it becomes possible to access a WORM type magneto-optical disk having a write protection function and a rewritable magneto-optical disk with the same magneto-optical disk drive. Accordingly, the magneto-optical disk drive finds a wider range of application, and it is also possible to reduce the media cost.
However, if an attempt is made to apply the same method to an optical disk system with only a rewritable type standard already set therein, such as a DVD-RAM, the following problem occurs.
The standard of the rewritable disk already exists, and such a disk is commercially available. An optical disk system for driving an optical disk in conformity with the standard also already exists. Even if media type data of the media type identification data area is newly defined, as in the example of the magneto-optical disk under such circumstances, it is not possible to change the existing drive. Therefore, it is impossible to control the operation of the existing optical disk drive having no write protection function.
Actually, as described above, all optical recording systems do not utilize media type identification data for discriminating the media types. Further, even if novel encoded data which has been undefined in the art is written to the media type identification data, the operation has been undefined because a conventional optical recording system cannot recognize the meaning of the encoded data.
Namely, in the prior-art example, there has been a risk that the data on the optical recording medium is corrupted by a mistake with the existing recording drive when a medium with a restriction on its function, such as a low-priced medium providing low overwrite cyclability is introduced.